The present invention relates to a process for producing polymers containing an oxetanyl group on the side chain which are utilizable for various reactions such as ring-opening polymerization and addition reaction. Furthermore, the polymers obtained by the process of the present invention can be used, for example, as a main component of ultraviolet-curing compositions which cure upon irradiation with ultraviolet rays.
The ultraviolet-curing techniques are very important in the industries such as coating for wood, coating for metals and printing taking advantage of high curing rate, good operability with requiring usually no solvents and very small energy quantity needed. Especially, it is known that ultraviolet-curing resins having an oxetane ring which is a 4-membered cyclic ether are much higher than epoxy resins in curing rate when irradiated with ultraviolet rays. Furthermore, it is expected that, when polymers represented by the formula (2) mentioned hereinafter which have an oxetanyl group on the side chain, said group having large ring-opening polymerizability, are used for ultraviolet-curing resins, the resulting resins are excellent in surface hardness and heat resistance.
The above polymers having an oxetanyl group on the side chain are produced by ring-opening polymerizing 3-[(oxiranylmethoxy)methyl]oxetane monomers represented by the formula (1) referred to hereinafter which contain an oxetane ring and an oxirane ring in the molecule. However, hitherto only cationic polymerization was employed and, therefore, both the oxirane ring and the oxetane ring simultaneously undergo ring-opening. As the result, the desired polymers having an oxetanyl group on the side chain are obtained in only very small yields.
An object of the present invention is to provide a process for producing, in high yields, polymers having an oxetanyl group on the side chain which can perform various reactions such as ring-opening polymerization and addition reaction.
The inventors have found that polymers having an oxetanyl group on the side chain and represented by the formula (2) can be produced by subjecting to anionic ring-opening polymerization a 3-[(oxiranylmethoxy)methyl]oxetane monomer represented by the formula (1) alone or together with other monomers having an epoxy group. 
wherein A represents a hydrogen atom or an alkyl group of 1-6 carbon atoms. 
wherein A is as defined above, and R represents a hydrogen atom, a chloromethyl group, straight chain alkyl group or branched chain alkylene group of 1-12 carbon atoms, phenyl group, straight or branched chain alkyloxymethyl group of 1-12 carbon atoms or phenoxymethyl group, and n and m each represent a molar fraction, n being 100 -1 mol %, m being 0-99 mol % with n+m=100.